The present invention relates in general to cooking equipment and relates more particularly to cooking equipment of the type where a cooking vessel is adapted to receive a liquid other than water, for example oil, to transfer heat to food products in the vessel. The vessel may be open top or closed top. Where closed top vessels are used the cooking process is many times carried out under pressure.
Regardless of whether the vessel is open top or closed top, the presence of water in the vessel can result in dangerous consequences.
Such cooking vessels have a very high heating rate so the contents of the vessel are heated rapidly.
Water can be introduced into such a vessel in a variety of ways. For example, vessels must be periodically cleaned and if the vessel is inadvertently operated in a cooking cycle during the cleaning process the water can be quickly brought to a boil, and even superheated, so that the water boils out of, or in the event of superheating even erupts, from the vessel. The heated water can then cause damage to personnel or property in the area of the cooking device. Because of the necessary heating capability of the cooker the water is not only heated rapidly to the boiling point but significant quantities of heat are added to the boiling water before it leaves the cooker causing further rapid expansion of the steam bubbles and increasing the rate of boilover.
Boilover, or eruption, of the water during the cleaning process where cleaning materials are present in the water is potentially more dangerous the boilover of water in several respects. This is because the cleaning materials modify the nature of the water and can themselves have characteristics which cause further injury to nearby personnel.
First, the presence of any solute in the water will alter the boiling point, and usually raise, the boiling temperature of the water. The increased boiling temperature of the solution alone presents significantly greater potential for injury.
Additionally, most such cleaning materials added to the water have a great potential for injury. For example most cleaning substances include caustic substances such as alkali hydroxides, or equivalent materials, as a base. Such materials alone have the capability to cause severe damage and can be even more dangerous when in a water solution.
For example sodium hydroxide, and most hydroxides have an exothermic reaction with water and when they come in contact with the skin, even in solution, draw water from the flesh and cause burns. If the solution is heated the effect is even more aggravated. Even worse, hydroxides in contact with flesh cause a condition known as "liquefaction necrosis" which includes protein-enzyme dissociation, a decrease in collegen content in the tissue, saponification of cell membrane lipids and cellular death. The extent of the damage is a function of a number of factors such as temperature, concentration and time of exposure.
The effects of exposure to cleaning solutions, particularly hot alkalis emitted from a cooking vessel in boiling water, can be severe. This is one problem which is addressed by the present disclosure.
In any event, the presence of water in the vessel during a cooking cycle is a potentially dangerous problem. One means for detection of circumstances which can lead to the dangerous situations is the subject of the present disclosure.
Other means are also known for the detection of foreign substances in the heat transfer liquid in a cooking process such as disclosed in my copending application Ser. No. 422,750.
Other prior art detection means relate to determination of physical characteristics of the heat transfer medium.
In general, such detection means rely on the measurement of characteristics which are dependent on the heating rate or other characteristic. It has been found that many such detection means are subject to false indication or failure to recognize the presence of the water in the heating medium for several reasons such as the fact they may fail to recognize the effects of agitation of the liquid in the vessel.
Further, in prior art arrangements the detection may be useful in applications where the water is the primary constituent of the material in the vessel and in other cases the detection device may work only when there is a mixture of water and oil in the vessel.
In the case of closed lid cookers the buildup of pressure because of the presence of water in the system is particularly dangerous. In most such cookers, a vent is employed to be closed to allow buildup pressure in the cooker. Operation of a vent to prevent buildup of pressure is also within the scope of the present invention.
Briefly no prior art detection system is known which takes advantage of characteristics of the water or water/oil mixture at the boiling point of water.